This invention relates to a high pressure sensor, and more particularly to a low cost stainless steel pressure sensor assembly that is integrated into a molded plastic component.
Motor vehicle controls frequently require measurement of certain pressure parameters such as engine oil pressure, fuel pressure, transmission fluid pressure or brake pressure. For reliability and durability, such applications usually require the use of a stainless steel pressure sensor element. In a typical application, the sensor element is welded to stainless steel a pressure port that is attached to the pressure vessel by a threaded fitting, for example. Due to the high cost of stainless steel relative to other materials, and the difficulty of machining stainless steel, various pressure port configurations have been developed for mininizing the required amount of stainless steel. See, for example, the U.S. Pat. Nos. 5,939,637 and 6,050,147, both of which are assigned to the assignee of the present invention. However, there is a growing interest in integrating a pressure sensor with the pressure vessel instead of attaching the pressure sensor to the pressure vessel by a threaded fitting, particularly in the case of molded plastic pressure vessels. Accordingly, what is needed is a pressure sensor assembly that minimizes the usage of stainless steel while being amenable to integration with molded plastic assemblies.
The present invention provides an improved pressure sensor assembly incorporating a stainless steel pressure sensing element, wherein the pressure sensing element is welded to a stainless steel pressure port that is insert-molded into a molded plastic pressure vessel. Sealing between the pressure port and the pressure vessel is enhanced by a O-ring seated in a groove on the outer periphery of the pressure port, or by a sealant applied to the periphery of the pressure port prior to the insert molding operation. According to the invention, the pressure port is insert-molded with the pressure vessel so as to expose an axial end of the pressure port having a stepped annular surface, and the pressure sensor element is welded to the exposed end of the pressure port. In a preferred embodiment, the plastic material of the pressure vessel extends into a central axial bore of the pressure port to minimize leakage by maximizing a potential leakage path for the medium contained by the pressure vessel, and over a shoulder of the pressure port to secure the pressure port in the body of the pressure vessel.